There is a current trend toward the use of a laser beam to provide guidance for certain vehicles, thereby eliminating the need for an attendant to guide them. Such a system is described in U.S. Pat. No. 4,790,402, which is owned by the assignee of the present invention.
U.S. Pat. No. 4,790,402 describes a vehicle on which is mounted a laser unit. This transmits a scanning beam which is reflected sequentially by each of a series of retroreflective targets mounted ahead of the vehicle along the desired pathway. The reflected beam returns to the laser unit on the vehicle and provides a course corrective signal by means of which the vehicle is caused to steer directly toward the target which is reflecting the beam. When the vehicle has nearly arrived at that target, the laser is caused to search out the next target ahead of the machine along the desired track and lock onto it. The vehicle is then caused to steer directly toward that target, and so on, until the intended pathway is completed.
With some types of vehicles it is advantageous to travel repeated parallel paths. For example, a floor maintenance machine such as a sweeper or scrubber is routinely driven along parallel paths, each of which is offset from its neighbor by a little less than the width of the machine. In this way an entire floor area may be cleaned. This is sometimes referred to as "region filling". The machine of U.S. Pat. No. 4,790,402 is a floor maintenance machine, and would be expected to operate on such parallel pathways. Its guidance system will keep the laser unit on the machine headed directly toward the next target. There is provision to move the laser unit from side to side on the machine, so one trip can be made with most of the machine to the left of the line of targets and the next trip can be made with most of the machine to the right of the line or vice versa. In this way an area nearly as wide as two widths of the machine can be cleaned by referring to one line of targets. If wider areas are to be cleaned, one or more additional lines of targets must be installed.